For over a hundred years, the etiopathogenesis of the pilonidal sinus was considered embryonic. This theory has now been abandoned. The pathogenesis is still not fully understood. It is currently believed to be of multifactorial origin. The pilonidal sinus forms as a dimple-like indentation in the gluteal cleft directly above the coccyx (DD: open neural tube). Here, mechanical stress, especially while sitting (jeep driver disease), causes stretching of hair follicles, which eventually rupture. With constant maceration, germs penetrate, leading to acute or chronic inflammation. The doughy soft tumor spreads through a widely used fistula system to the sides and in extreme cases also to the anus.
One or more of the following factors is a risk factor for the development of a pilonidal sinus:
- Heavy hair growth Theory: through a drill effect, broken hairs are driven into the skin, the driving force being the rolling movements of the hairs between the buttocks (especially when sitting). The hair follicle is closed by sitting and becomes infected. However, 50% of affected patients do not exhibit excessive hairiness.
- Deep gluteal fold (overweight)
- Local irritation
- Positive family history
- Age 15-25 Theory (according to Bascom): Sex hormones during puberty lead to changes in the hair appendage glands. Microscopically, enlarged hair follicles can then be detected. With simultaneous increase in the buttocks (fat/muscle), tensile forces on these follicles are increased, especially near the sacrococcygeal joint (site of the greatest bend). The so-called "pits" are formed. Sitting raises the skin over the gluteal cleft. This causes the base of the follicle to tear with the addition of impact (unbuffered seat, sports), and then by a "kind of suction" loose hairs and/or keratin can be sucked into the pit. However, pilonidal sinus also occurs in non-adolescents.
The principle of the Karydakis operation is:
- Flattening of the gluteal fold
- Lateralization of the surgical wound away from the gluteal cleft. Studies have shown that scar formation in the midline tends to significantly more recurrences, prolonged healing, and an increased infection rate.
Advantages of the technique are:
- Thick skin flap
- Simple surgical technique
Disadvantage:
- Large skin defects cannot be closed without tension. Here, a rotational flap, e.g., according to Limberg, is more sensible.